The present invention relates to the general field of turbomachine rotor disks that are provided at their peripheries with slots in which blade roots are mounted. The invention relates more particularly to a device enabling such slots to be cooled effectively.
In known manner, the disks of a turbomachine rotor, such as the disks in the various stages of the low pressure turbine, include at their periphery a plurality of substantially axial slots into which the roots of moving blades of the turbine are engaged.
While the turbomachine is in operation, the flow section of the low pressure turbine in which the blades are disposed passes gas at a temperature that is very high. The slots in the disk that receive the blade roots are therefore directly exposed to the hot gas so it is necessary to cool them in order to avoid any damage to the disks.
For this purpose, it is known to take a fraction of the air that flows outside the flow section of the low pressure turbine and direct it via a cooling circuit to the slots in the rotor disks. In practice, each rotor disk has an annular flange that extends upstream from the upstream radial face of the disk and around which there is mounted a retaining annulus. The disk flange and the retaining annulus are disposed in such a manner as to form between them an annular space forming a cooling air diffusion cavity. This diffusion cavity is fed with cooling air at its upstream end via a plurality of orifices that are regularly distributed around the axis of rotation of the disk, and at its downstream end it opens out into the bottom of each of the slots in the disk. Air that flows outside the flow section of the turbine penetrates into the diffusion cavity of the cooling circuit via orifices, diffuses in said cavity, and then ventilates the slots in the disk in order to cool them.
Nevertheless, that type of cooling circuit does not enable completely uniform cooling to be obtained for all of the slots in the rotor disk, which is harmful for good operation of the disk, and thus for the lifetime of the disk. It will readily be understood that with such a configuration, the slots that are disposed directly in line with the air speed orifices of the cooling circuit are cooled considerably better than the slots that are angularly offset further away therefrom.